1. Field of the Invention
The present invention relates to an image forming apparatus such as copying apparatus or laser beam printer (LBP) and, more particularly, to an image forming apparatus in which a transfer unit having a belt and a cleaning device is detachable for an apparatus main body.
2. Description of the Related Art
Hitherto, there has been known a color image forming apparatus in which toner images formed on photosensitive drums of a plurality of process cartridges are primarily transferred onto an intermediate transfer belt in each primary transfer unit and the toner images on the intermediate transfer belt are secondarily transferred onto a recording material in a secondary transfer unit.
In such an image forming apparatus, toner remaining on the intermediate transfer belt after the secondary transfer is removed by a cleaning device and collected into a drain toner collecting tank. Japanese Application Laid-Open No. 2001-075374 has proposed such a technique that the cleaning device and the intermediate transfer belt are integrated as an intermediate transfer unit so as to be detachable for the image forming apparatus main body. Thus, the drain toner can be collected without any leakage and the maintenance operation such as repair, inspection, and exchange of the intermediate transfer belt, and cleaning device can be easily executed.
An image forming apparatus having such an intermediate transfer unit is illustrated in FIGS. 10 and 11. As illustrated in FIG. 10, an intermediate transfer unit 50 is arranged from one side of an image forming apparatus main body to the other side. In the intermediate transfer unit 50, a plurality of process cartridges 53 is arranged under an intermediate transfer belt 51. Further, in the intermediate transfer unit 50, a cleaning device 52 is integratedly fixed to one end portion of the intermediate transfer belt 51 so as to be juxtaposed with the process cartridge 53. On the side (left side of the apparatus main body in the diagram) where the cleaning device 52 has been arranged, as illustrated in FIG. 11, an opening portion 54 is formed so that the intermediate transfer unit 50 can be pulled out. An opening/closing member 55 for covering the opening portion 54 is provided so that it can be freely opened and closed. Thus, the intermediate transfer unit 50 can be pulled out in the horizontal direction from the cleaning device 52 side.